Narrow-Row Seed-Yield Enhancement in Determinate Soybean
- J. E. Board ,
- B. G. Harville and
- A. M. Saxton
Although many studies have been conducted to determine the effect of narrow vs. wide rows on determinate soybean [Glycine max (L) Merr.] yield, little information is available explaining why these yield responses occur. This research was conducted to determine the roles of reproductive partitioning, light interception duration (LID), and total dry matter duration (TDMD) between emergence to R5 (E-R5) and R5 to R8 on narrow-row seed-yield enhancement. Field studies were conducted using normal and late planting dates, two commercial soybean cultivars, and 100- (wide) and 50-cm (narrow] row spacings during 1987 and 1988 at Baton Rouge, LA on a Mhoon silty clay (fine-silty, mixed, nonacid, thermic Typic Fluvaquent) soil, Significant narrow-row seed-yield enhancement occurred from both planting dates, but the increases were much larger at the late date. In the normal planting, seed yield was strongly correlated with LID (R5-R7) (r2 = 0.77, P = 0.001) and TDMD(R5-R8) (r2 = 0.86, P = 0.001), but not LID(E-RS) or TDMD(E-RS). In the normal planting, significant narrow-row seed-yield enhancement occurred only in cases in which narrow rows achieved 95% light interception before pod filling, but wide rows did not. In contrast, seed yield in the late planting was highly correlated to LID(E to R5) (r2 = 0.85, P = 0.001) and TDMD(E-R5) (r2 = 0.81, P = 0.001), as well as LID(R5-R7) (r2 = 0.98, P = 0.001) and TDMD(R5-R8) (r2 = 0.94, P = 0.001). Although narrow-row yield enhancement in the late planting was greatest when LID and TDMD were stimulated both before and after R5, significant yield increases in narrow versus wide rows occurred even in cases in which LID R5 to R7 differences were too small to affect TDMD(R5-R8). In conclusion, narrow-row seed-yield enhancement of late plantings was influenced by increased LID and TDMD throughout the season, whereas only LID and TDMD enhancement during pod filling of normal plantings affected narrow-row seed-yield increases.
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